<p>The objective of this study was to evaluate the effect of boron (B) supplementation on bone health markers, antioxidant and immune status in growing heifers. Twenty-four Hariana heifers (10 to 24 months of age) were distributed into four groups, each consisting of six animals, by a 2 × 2 factorial design. The control group (C1) received a basal diet, while the experimental groups received either normal calcium (Ca) with 200 ppm boron (T1), low calcium (30% less than normal) without boron (C2), or low calcium with 200 ppm boron (T2). The heifers were offered a basal diet to experimental groups containing 50% concentrate, 35% wheat straw, and 15% green fodder to meet nutrient requirements. Results showed no significant differences in DMI, nutrient digestibility, and body weight gain as well as plasma total immunoglobulin (TIg) level. Boron supplementation significantly influenced antioxidant status, with higher FRAP levels in T1 compared to the control, and the lowest FRAP in C2. SOD activity showed no significant change across groups. Plasma osteocalcin levels were higher in the T1 and T2 groups, indicating a potential improvement in bone health. However, the activity of other bone markers, such as BALP and TRAP, was not significantly affected. Plasma calcium concentrations were similar between T1 and T2, with a decrease in C2, while plasma boron concentrations were significantly higher in T1 and T2 compared to C1 and C2. It may be concluded that boron supplementation at 200 ppm, regardless of calcium levels, improved bone health markers, antioxidant status, and calcium utilization in growing heifers, without affecting growth performance or nutrient digestibility.</p>